[Heat production from reaction of inhalation anesthetics with dry soda lime].
There are some case reports about excessive heat production in the absorbent canister when sevoflurane or enflurane are washed into a circle containing dried soda lime. This observation was often made in the DRAGER ISO 8 circle system with the gas inlet upstream of the soda lime canister with the gas-flow from bottom to top.


METHODS
The temperature in the center of an absorbent canister was measured 3.0 cm and 7.5 cm above the bottom. Soda lime (DRAGERSORB 800) was dried in an O2 stream for 2-3 days until there was no further loss in weight. 5 Vol% of desflurane, enflurane, isoflurane and sevoflurane in 2 1/min O2 or 4 Vol% of halothane in 2.5 I/min O2 were continuously fed into the canister. The concentration of the respective inhalational agents were measured after the soda lime canister using a DATEX Capnomac. Experiments were performed at ambient temperatures of 20-22 degrees C.


RESULTS
A considerable temperature increase was achieved with all anaesthetics. The highest temperatures were measured at the upper sensor with 56-58 degrees C for desflurane, 76-80 degrees C for enflurane and isoflurane, 84-88 degrees C for halothane and 126-130 degrees C for sevoflurane. IR-detection for some agents was considerably delayed or the time course indicated that other compounds might have formed which absorb at the wavelength monitored.


CONCLUSIONS
The high temperatures indicate the degradation rather than absorption of the volatile anaesthetics. CO is known to be degradation product of all currently used volatile anaesthetics except sevoflurane. Sevoflurane, however, produced the highest temperatures passing through dried soda lime. There are no reports about new specific breakdown products for sevoflurane on dried soda lime.
Wissing
H
H
Zentrum für Anaesthesiologie und Wiederbelebung, Klinikum der J.W. Goethe Universität Frankfurt.
Kuhn
I
I
Dudziak
R
R
D018685:Anesthetics, Inhalation / Q000737:chemistry*; D017610:Calcium Compounds / Q000737:chemistry*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004349:Drug Packaging; D006358:Hot Temperature; D010087:Oxides / Q000737:chemistry*; D012972:Sodium Hydroxide / Q000737:chemistry*; D013055:Spectrophotometry, Infrared
D018685:Anesthetics, Inhalation; D017610:Calcium Compounds; D010087:Oxides; C004569:soda lime; D012972:Sodium Hydroxide
Zur Temperaturentwicklung von Inhalationsanästhetika auf trockenem Atemkalk.